(1) Field of the Invention.
The present invention relates to a front suspension for motorcycles, and particularly a suspension employing a four-bar linkage.
(2) Description of the Prior Art.
Conventional front suspensions for motorcycles which have generally been employed are of the telescopic type in which each front fork is constructed of an expansion fork pipe and a pair of bottom cases. A new type of suspension is disclosed in U.S. Pat. No. 4,212,481 issued July 15, 1980. Such suspension has a front fork comprising an upper fork rotatably pivoted on the body of the motorcycle and a lower fork supporting the front wheel. These two forks are connected on either side by a front and a rear arm so as to define a four-bar linkage. The vertical movement of the front wheel following the undulations of the road is allowed by the transformation of the linkage. Movement of the front axle can be controlled so as to move along a straight path and approximately parallel to the axis of rotation of the handle bar by arranging the front and rear arms diagonally and converging downwardly. A shock absorber for absorbing and damping the movement of the front wheel caused by the transformation of the linkage is located between two members chosen from among the two arms and the lower fork, or between the upper fork and a member chosen from among the two arms and the lower fork.
Advantages provided by the aforesaid new suspension of the four-bar linkage type are, firstly, that the front wheel is allowed to move more smoothly and an increased rigidity is provided for the suspension compared with the telescopic type suspension wherein a sliding resistance is generated between the fork pipe and the bottom cases during the extension and the contraction of the suspension since the suspension comprises a linkage. Secondly, that the performance of the front wheel in following road irregularities is improved since a long stroke of the front wheel is permitted. Also, only a short stroke is sufficient for the shock absorber while a long stroke of the front wheel is permitted, thereby requiring only a small-sized and lightweight shock absorber.